Update needed for Rust v1.77.0

error: field `0` is never read
   --> system/security/keystore2/src/database.rs:848:31
    |
848 | pub struct PerBootDbKeepAlive(Connection);
    |            ------------------ ^^^^^^^^^^
    |            |
    |            field in this struct
    |
    = note: `-D dead-code` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(dead_code)]`
help: consider changing the field to be of unit type to suppress this warning wh
ile preserving the field numbering, or remove the field
    |
848 | pub struct PerBootDbKeepAlive(());
    |                               ~~

error: aborting due to 1 previous error


Bug: 330185853
 ./test_compiler.py --prebuilt-path dist/rust-dev.tar.xz  --target aosp_cf_x86_64_phone --image

Test: m rust
Change-Id: I4cb81c955372c4f8f50b940b389f2d7cfc5d3ce9
diff --git a/keystore2/src/database.rs b/keystore2/src/database.rs
index f343cb3..113c049 100644
--- a/keystore2/src/database.rs
+++ b/keystore2/src/database.rs
@@ -845,6 +845,7 @@
 /// Shared in-memory databases get destroyed as soon as the last connection to them gets closed.
 /// This object does not allow access to the database connection. But it keeps a database
 /// connection alive in order to keep the in memory per boot database alive.
+#[allow(dead_code)]
 pub struct PerBootDbKeepAlive(Connection);
 
 impl KeystoreDB {